Embodiments generally relate to wireless local area networks (WLAN), and in particular, to power saving for one or more client devices in a wireless network.
Some wireless networks are based on a cellular architecture where the system is subdivided into wireless network cells. One type of wireless network cell, known as a basic service set (BSS), contains client devices controlled by a wireless network access point (AP), and another type of wireless network cell, known as an independent basic service set (IBSS), contains client devices which are not controlled by an access point. A service set identifier (SSID) is a label or name that distinguishes one wireless network from another. Client devices use the SSID to establish and maintain connectivity. Wireless access points of different BSSs may be connected via a distribution system (DS) that is usually a wired network. The entire interconnected WLAN network, including the different WLAN cells, their respective WLAN access points and the distribution system is known as an extended service set (ESS).
A client device may, or may not, be battery-powered. For example, a client device, such as a wireless-enabled laptop, a wireless-enabled cellphone, a wireless-enabled personal digital assistant (PDA), and the like, may sometimes be battery-powered, and at other times may receive power from an external source, such as a power outlet. Other client devices, such as a desktop computer, may receive power from an external source, such as a power outlet, and may not have the option to be battery-powered. It may be beneficial to enhance the battery lifetime of battery-powered client devices.
A client device having two or more connection profiles may scan for wireless local area networks matching the profiles in sequence, and if no successful connection is achieved then the client device may go into a sleep state for a sleep interval (e.g., a few seconds) before trying to scan the profiles again. While a device is not in coverage and is scanning for wireless local area networks, the average amount of charge drawn from its battery may be related to the ratio between the time spent in the sleep state and the time spent scanning. For a device with N profiles, an exemplary sequence for scanning/sleeping may be as follows:P1P2 . . . PN Sleep1 P1P2 . . . PN Sleep2 P1P2 . . . PN Sleep3 P1P2 . . . PN Sleep4 P1P2 . . . PNwhere Sleep1, Sleep2, . . . are sleep intervals between profile scanning intervals, and the duration of sleep intervals may be increased (that is, Sleep1<Sleep2<Sleep3< . . . ) until it reaches an upper limit. The more user profiles the device is scanning for, the lower the ratio between the time spent in the sleep state and the time spent scanning. This may have an adverse effect on the battery life of the device. For example, an exemplary wireless client device that is not in coverage may have a battery life of five days if scanning for one profile, three days if scanning for two profiles, and one and a half days if scanning for three profiles.
It will be appreciated that for simplicity and clarity of illustration, elements shown in the figures have not necessarily been drawn to scale. For example, the dimensions of some of the elements may be exaggerated relative to other elements for clarity.